Battery electrodes may be made of sintered metal powder and may have sintered metal base with an active material filled into the micropores, such as discussed in U.S. Pat. No. 3,488,220. Or the sintered metal may itself be the electrode active material. It has also been disclosed to form a porous electrode matrix by sintering, with the electrode then being attached to a base plate. In U.S. Pat. No. 4,091,184, it is disclosed to deposit silver oxide onto an intercell connector to form a porous matrix of silver oxide which is then dried, sintered, pressed and recharged to form a positive electrode.
Another technology relying on a porous matrix and eventually leading to battery electrode development, while ostensibly having at least partial prior art origins in U.S. Pat. No. 3,549,505, was developed from metallized foams. In this '505 patent a reticulated polyurethane foam having interconnected cells is coated with a conductive material followed by electroplating. Optionally, pyrolysis can follow the elctroplating to decompose the underlying polyurethane skeleton. Directly stemming from this as a general development, a metallizing method improvement was disclosed in U.S. Pat. No. 4,077,853. As discussed therein, after the nickel-electroplating step, the material was pyrolyzed under a hydrogen reducing atmosphere resulting in a ductile metallized foam. This material was discussed in the '853 patent as being useful for battery plates. In a corollary general development, taught in U.S. Pat. No. 3,694,325 for preparing materials that might be useful as electrodes, it was disclosed to subject the metallized foam after the nickel plate to a first heating step at 800.degree. F. (427.degree. C.) in an oxidizing environment and subsequently to anneal the metal in a reducing atmosphere at a temperature of at least about 1400.degree. F. (760.degree. C.)
Referring still to such technology, but as tailored more particularly to battery electrode application, developments include techniques as have been disclosed in European Patent Application No. 071,119. The process disclosed therein involves temperatures of essentially ambient to only slightly above ambient. In this development, nickel oxide is impregnated in the nickel plated open cell material and subsequently compressed in electrode preparation.
Referring still to battery electrode preparation, but in a development involving pyrolysis, a resin impregnated with carbon to aid coating ease, after electroplating, is next roasted for resin removal. It is then annealed in a reducing environment, all as taught in U S. Pat. No. 4,251,603. Thereafter, a paste of nickel hydroxide can be used for filling the porous nickel structure thus prepared.
There is, nevertheless, a need for preparing battery components which can be high in active material utilization. This aspect of desirable utilization should be coupled with ruggedness of structure, permitting augmented charge-discharge cycles without deleterious loss of structural integrity. Such combination would be most desirable for providing multiple uses of the electrode.